1. Field of the Invention
The present invention pertains to rotary fluid handling devices such as radial turbines, turbo-expanders, centrifugal compressors, and the like comprising a stationary body or stator enclosing a rotor having a plurality of openings extending radially thereinto. The radial openings may each form one end of a respective flowway curved so that the opposite ends thereof are substantially axially directed, or the radial openings may all communicate with a common generally axial channel. Annular seals are typically provided on both sides of the radially directed ends of these flowways. These seals are typically of the labyrinth type through which leakage occurs. The fluid thus leaking through the seals often contains entrained dust and other particles, particularly at start-up of the machine.
Such particles leaking past one of the seals may become trapped in the area behind the rotor. Even when passages through the rotor are provided for the purpose of venting this area to the "eye" of the rotor, the particles are not removed therethrough. This is because the natural flow patterns of the particles will not carry them into the rotor passages. Centrifugal force also keeps the particles in circulation so that eventually they erode the seal and/or the adjacent areas of the machinery cooperative therewith.
2. Description of the Prior Art
In the past, several systems for dealing with this erosion problem have been developed, but none has been entirely successful. One of these attempted to intercept and collect the particles before they reached the seal and direct them into the rotor discharge or to some other suitable site. In other prior systems, large pockets were provided upstream of the seal which the particles could enter and "get lost." The failure of such approaches was due to the fact that they were dependent on removal of the particles before they reached the seal. Since complete removal of the particles in this manner was impossible, some particles would still leak past the seal, become trapped behind the rotor, and erode the seal area while being circulated by centrifugal force, etc.